<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>删除事件</title>
    <style>
        div {
            width: 200px;
            height: 200px;
            background: pink;
        }
    </style>
</head>
<body>
    <div>1</div>
    <div>2</div>
    <div>3</div>
    <script>
        // 传统方式删除事件
        var divs = document.querySelectorAll('div')
        divs[0].onclick = function() {
            alert(11)
            divs[0].onclick = null;
        }
        // 2. removeEventListener 删除事件
        divs[1].addEventListener('click',fn) 
        function fn() {
            alert(22)
            divs[1].removeEventListener('click',fn)
        }
        //  3. 
        divs[2].attachEvent('onclick',fn1);
        function fn1() {
            alert(33);
            divs[2].detachEvent('onclick',fn1)
        }
    </script>
</body>
</html>